Method for smoothing substrate surface

ABSTRACT

Methods for modifying contours of substrate surfaces are disclosed. Methods include depositing filler material on a critical mating surface of a substrate so as to render the mating surface more mateable with a matching substrate. The filler material can be deposited within or around features or defects on the mating surface such that a final desired surface contour is achieved. In some cases, the final surface contour of the mating surface is planar. This can prevent gaps associated with the features or defects from forming between the substrate and the matching substrate when they are joined together. The final surface contour of the mating surface can be determined by comparing dimensions of the mating surface to dimensions of a reference surface. In some cases, ink jet printing techniques are used to deposit the filler material accurately in prescribed locations and with precise thickness control.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation patent application of U.S. patentapplication Ser. No. 14/815,499, filed Jul. 31, 2015 and titled “Methodfor Smoothing Substrate Surface,” now U.S. Pat. No. 10,350,634, thedisclosure of which is hereby incorporated herein by reference in itsentirety.

FIELD

The described embodiments relate generally to methods for smoothingsurfaces of substrates. More particularly, the present embodimentsrelate to creating mateable surfaces by depositing material in or aroundsurface defects of substrates.

BACKGROUND

Cutter marks, scratches, pits, dents or other surface defects are verycommon in the manufacturing of parts. Some of the surface defects arerelated to the handling of the parts during the manufacturing process.Some surface defects are related to the machining process itself. Forexample, a manufacturing tool and/or part can shift during a machiningoperation, causing unintended marks or inconsistencies on the surface ofthe part. Some surface defects are related to manufacturing tolerancesthat are inherent to the machining process. In some cases, certainmaterials, such as soft, malleable or brittle materials, can beespecially susceptible to acquiring certain types of surface defects.

One of the problems associated with surface defects relates to themanufacture of mating components of a part. In particular, surfacedefects can cause uneven mating surfaces of matching parts. For example,a cutter tool can create divots or channel shaped defects that aresub-flush to surrounding surfaces. These divots or channels can preventintimate contact between mating surfaces, which in turn can lead toformation of a noticeable gap between the mating components, adverselyaffecting the cosmetic appearance of the part. In addition, this canlead to poor sealing and poor adhesion of the mating components, whichnegatively affects the reliability and functionality of the part. Thesedefects, if not repaired, may also be carried forward and causeprocessing problems or failures in later manufacturing stages.

SUMMARY

This paper describes various embodiments that relate to manufacturingtechniques for forming smooth mating surfaces on parts. In particularembodiments, non-contact additive processes, such as printing techniquesor robot-controlled needle dispensing techniques, are used to preciselydeposit material in and/or around surface defects so as to formconsistently smooth surfaces for mating with corresponding parts.

According to one embodiment, a method of adjusting a surface of asubstrate is described. The method includes comparing a contour of thesurface to a reference contour of a reference surface. The method alsoincludes, based upon the comparing, identifying a portion of the surfacehaving a corresponding surface contour that is out of conformance withrespect to the reference contour as: (1) a bump when the correspondingsurface contour is proud of the reference contour, otherwise (2) as adivot. The method further comprises bringing the corresponding surfacecontour of the identified portion into conformance by: depositing afirst amount of filler material in a region around the bump, otherwise,depositing a second amount of filler material into the divot.

According to another embodiment, a method of modifying a mating surfaceof a substrate is described. The mating surface is arranged to bond withan inlay. The method includes comparing a shape of the mating surface toa shape of a reference surface of the substrate. The reference surfaceis associated with an external surface of the substrate. The method alsoincludes depositing a filler material on the mating surface such thatthe mating surface takes on the shape of the reference surface. When theinlay is bonded to the mating surface, an external surface of the inlayis substantially flush with the external surface of the substrate.

According to a further embodiment, a method of modifying a housing isdescribed. The substrate has a perimeter defined by a lip portiondefining dimensions of an opening for accommodating a cover glass. Themethod includes obtaining dimensional data related to the housing. Themethod also includes depositing a filler material on a surface of thelip portion so as to decrease the dimensions of the opening inaccordance with the dimensional data of the cover glass.

These and other embodiments will be described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements.

FIG. 1 shows an internal surface of a housing section of a consumerdevice having mating surfaces.

FIGS. 2A-2G show a portion of the housing section of FIG. 1 having arecessed feature undergoing a surface modification process.

FIGS. 3A-3E show a portion of the housing section of FIG. 1 having aprotruding feature undergoing a surface modification process.

FIGS. 4A-4D show a portion of the housing section of FIG. 1 having adifferent protruding feature undergoing a surface modification process.

FIGS. 5A-5E show a portion of the housing section of FIG. 1 having arecessed inlay region undergoing a surface modification process.

FIG. 6 shows perspective and cross section views of mateable housingsections after undergoing a surface modification process.

FIGS. 7A-7C show cross section views of a feature undergoing a featuremodification process and a surface modification process.

FIG. 8 shows a flowchart illustrating a method of modifying a surface inaccordance with some embodiments.

FIG. 9 shows a flowchart illustrating another method of modifying asurface in accordance with some embodiments.

FIG. 10 shows a flowchart illustrating a further method of modifying asurface in accordance with some embodiments.

FIG. 11 shows a block diagram of an electronic system suitable for usewith some described embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following descriptions are not intended to limit the embodiments toone preferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims.

The following disclosure relates to depositing filler material on asurface of a part to modify surface qualities such as the smoothness ofthe surface. The methods can be used to smooth out defects withinsurfaces of the part formed, for example, during previous machining orother manufacturing operations. The defects can be in the form of cuttermismatch regions, cutter marks, scratches, dents, or pits. The methodsare particularly useful for creating better mating surfaces between twoor more matching parts that are to be coupled together. The smoothermating surfaces can create a better wetting surface for applyingadhesives and reduce the occurrence of undesirable gaps between thematching parts.

The size of the defects can vary widely. For example, the defects can bevery small, e.g., on the scale of micrometers, or relatively large,e.g., on the scale of millimeters or even centimeters. In addition, thetypes and shapes of the defects can vary. For example, the defects canhave sharp or irregular corners and edges, can protrude from or recedewithin a surface of a part, or can simply be a gradual non-planarsection of the part. Thus, in particular embodiments, the methodsinvolve continuously adapting the depositing process to accommodatedifferent defect types and shapes. For example, the filler material canbe deposited in an additive manner providing for precise dimensioncontrol.

In particular embodiments, the methods involve precise control ofdepositing filler material using non-contact additive processes.Suitable non-contact processes can include ink jet printing techniqueswhere the filler material is ejected in small droplets. In someembodiments, a robot-controlled needle dispensing technique is used. Insome embodiments, the filler material is an ink material, such as apolymer-based ink. The printed-on filler material can be deposited in asingle pass or in incremental layers resulting in a substantially smoothsurface across the surface of the part. The printed-on filler materialcan also correct for manufacturing tolerances or intentional featuresthat may be an inherent consequence of a manufacturing process. Theprinted-on filler material can also be deposited in select regions tostrengthen a part, particularly during a manufacturing process.

In a particular embodiment, a method of detecting and correcting defectsis disclosed. The method involves inspecting the surface of the part fordefects using, for example, an optical imaging, a laser scanning, and/ora profilometry. In some cases, two- or three-dimensional data of thesurface is collected. The surface may be a planar surface or a curvedsurface. The defects can then be analyzed to determine if the defectshave correctable dimensions. If correctable, the surface can be modifiedby precisely depositing filler material in or around the defects. If thedefect is recessed, such as a scratch or a dent, the filler material canbe precisely printed into the recess either in multiple layers or in asingle pass, resulting in a substantially planar surface across thesurface of the part. If the defect is a protrusion, filler material canbe precisely deposited adjacent to the protrusion continuously or instepped layers, resulting in a smooth transition from the surface of thepart to the top of the protrusion. If the part contains multipledefects, the modification process can be repeated for each of thecorrectable defects. The surface modifications can then be inspected toensure that the modifications are within allowable tolerances. Ascanning inspection may be used to create a map of the modified surface,and the modifications can be compared against acceptable tolerances. Thetolerances may include surface smoothness and planarity across themodification, adhesion of the filler material to the part, and colormatching to the surface of the part. The part can also be reworked ifthe modifications are not acceptable.

Methods described herein are well suited for providing cosmeticallyappealing and/or functional parts of consumer products. For example, themethods described herein can be used to modify support structures andenclosures or portions of enclosures for electronic devices, such ascomputers, portable electronic devices, wearable electronic devices andelectronic device accessories, such as those manufactured by Apple Inc.,based in Cupertino, Calif.

These and other embodiments are discussed below with reference to FIGS.1-11. However, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these Figures is forexplanatory purposes only and should not be construed as limiting.

FIG. 1 shows a front view of an internal surface of housing section 100of a consumer device. Housing section 100 can correspond to a portion ofa housing for an electronic device, such as a portable computer, such asa laptop computer. Housing section 100 can be made of any suitablematerial, such as one or more of metal, plastic, ceramic, and glassmaterials. In a particular embodiment, housing section 100 is made of acontinuous metal material, such as aluminum or aluminum alloy, whichgives housing section 100 a seamless and continuous look and feel. Inaddition, metal material can make housing section 100 heat conductive,and therefore can act to disperse heat generated from electroniccomponents housed within housing section 100. In some embodiments, anelectrical conductivity of the metal material allows for grounding forone or more of the electrical components.

Housing section 100 includes mating surface 102 (indicated with hatchmarks) that is configured to mate with a corresponding second housingsection (not shown) to enclose one or more electronic components. Matingsurface 102 can be formed using one or more machining operation, such ascomputer numerical code (CNC) machining operations. Housing section 100can be secured to the corresponding second housing section usingfasteners, such as screws, bolts, etc. In some embodiments, adhesive isapplied between housing section 100 and the corresponding second housingsection at mating surface 102 to provide a sealed coupling betweenhousing section 100 and corresponding second housing section. In someembodiments, mating surface 102 is optimally planar so as to providegood bonding with the adhesive and proper sealing with the correspondinghousing section.

Mating surface 102 may include a number of areas that are uneven due toimperfect machining processes. For example, bump 106 may protrude asmall distance from mating surface 102. Furthermore, protruding features108 may each have a sloped top surface that are not coplanar with matingsurface 102. These types of discrepancies can cause non-ideal mating andsealing of housing section 100 with the corresponding second housingsection. Housing section 100 can include a number of other non-ideallyshaped surfaces. For example, recessed feature 104 at corner region 112a of housing section 100 may be unintentionally formed due to imperfectmachining processes. In some embodiments, an overall shape of housingsection 100 is embodied as a reference datum where parts of matingsurface 102 are used as a reference surface characterized as having areference contour. This will be described later below. Additionally,inlay region 110 may have an uneven mating surface with respect to acorresponding inlay.

The methods described herein involve depositing filler material ontohousing section 100 to correct for non-ideally shaped surfaces, such asrecessed feature 104, bump 106, protruding features 108, and inlayregion 110. In some embodiments, housing section 100 is translated intwo or three dimensions with respect to a deposition apparatus in orderto deposit filler material onto each of recessed feature 104, bump 106,protruding features 108, and inlay region 110. In some embodiments, aportion of the deposition apparatus (e.g., printer head or nozzle) istranslated in two or three dimensions with respect to housing section100 in order to deposit filler material onto each of recessed feature104, bump 106, protruding features 108, and inlay region 110. Themethods described herein can also be used to deposit filler material onor in intentionally formed features of housing section 100. For example,some features can be formed near corner regions 112 a, 112 b, 112 c, 112d to increase the structural integrity of housing section 100 nearcorner regions 112 a, 112 b, 112 c, 112 d. These and other embodimentswill be described in detail below.

FIGS. 2A and 2B show a front view and a cross section view,respectively, of recessed feature 104 of housing section 100. Recessedfeature 104 can be referred to as a divot, trench, dent, depression,pit, etc. Housing section 100 includes two recessed features, recessedfeature 104 and second recessed feature 202. Note that the cross sectionview of FIG. 2B shows a cross section view of recessed feature 104 butnot second recessed feature 202. Recessed features 104 and 202 can beunintentionally formed artifacts of a machining process or can beintentionally formed within housing section 100. In some embodiments,recessed features 104 and 202 are undesirable features formed withinhousing section 100 due to imperfect machining processes. For example,recessed features 104 and 202 can be formed due to mismatching ofcutters used in a machining process. Recessed features 104 and 202generally have very small depths. For example, recessed feature 104 canbe sub-flush to surrounding surfaces by a distance d of about 50micrometers or less.

The methods described herein can be used to fill in recessed features104 and 202 such that they are no longer sub-flush with surroundingsurfaces. To illustrate, FIGS. 2C-2F show cross section views ofrecessed feature 104 undergoing a surface smoothing process inaccordance with some embodiments. FIG. 2C shows recessed feature 104after first layer 212 a of filler material is deposited within recessedfeature 104. In some embodiments, first layer 212 a is deposited usingan ink jet printing process whereby the filler material is ejected froma nozzle in small droplets. This can provide accurately location (xy)and thickness (z) of first layer 212 a. For example, one or more nozzlesof an ink jet type printer can be scanned or passed over recessedfeature 104 to selectively deposit first layer 212 a within recessedfeature 104 without significant deposition on raised mating surface 204and/or channel 208. In a particular embodiment, an adjustable X-Ytranslation stage is attached to a printer table of the printer in orderto obtain accurate depositing of the filler material.

The filler material of first layer 212 a can be any suitable material.For example, the filler material can be an ink. The ink can be selectedfor desirable characteristics such as adhesion to housing section 100,adhesion to a subsequently added adhesive, the integrity of the ink oncedeposited, the viscosity of the ink, color and/or electricalconductivity. The consistency and viscosity of the ink can be chosen toprovide a particular purpose. For example, the ink can include a bindermaterial that increases the viscosity and provides volume to first layer212 a. In one embodiment, the binder material includes transparent(clear) or partially transparent ink. In some embodiments, the fillermaterial of first layer 212 a also includes one or more dyes that givefirst layer 212 a a particular color, such as black. In someembodiments, the ink is substantially non-electrically conductive whilein other embodiments the ink is electrically conductive. The ink can bea polymer-based ink suitable for use with an ink jet printer. The inkmay be an ultraviolet (UV) curable ink, where the ink is deposited inliquid form and then hardened by exposure to UV light once deposited onhousing section 100. In some embodiments, the volume of deposited inkdoes not change during curing of the ink. Alternatively, the ink may bea solvent ink where the volume of ink decreases during the curing of theink. In some embodiments, first layer 212 a has a viscosity that is lowenough to allow first layer 212 a to conform to a shape of recessedfeature 104 while in liquid form, and remain in the conformal shape oncehardened into solid state. The thickness of first layer 212 a can varydepending on the material of the filler material, the size of thedroplets formed by the ink jet printer and a desired thickness of firstlayer 212 a. In one embodiment, the thickness of first layer 212 aranges from about 5 and 10 micrometers.

FIG. 2D shows recessed feature 104 after multiple layers 212 a, 212 b,212 c of filler material have been sequentially deposited withinrecessed feature 104. Collectively, layers 212 a, 212 b, 212 c can bereferred to as filler material 212. Layers 212 a, 212 b, 212 c can bedeposited by passing or scanning the nozzle of the ink jet printer overrecessed feature 104 a number of times, with a layer of filler materialbeing deposited with each pass. In some embodiments, each of layers 212a, 212 b, 212 c is allowed to conform while in liquid form to the wallsof recessed feature 104 and hardened. The number of layers 212 a, 212 b,212 c can be chosen such that a final thickness of filler material 212is about the same as distance d that recessed feature 104 recesses belowthe adjacent surface of channel 208. That is, a top surface of fillermaterial 212 can be substantially flush with a top surface of adjacentchannel 208. In this way, top surfaces of filler material 212 andchannel 208 can cooperate to form a substantially planar mating surface214.

The number of layers 212 a, 212 b, 212 c required to make mating surface214 substantially planar can vary depending on the thickness of eachlayers 212 a, 212 b, 212 c. In some embodiments, filler material 212includes only one layer. In some embodiments, each of layers 212 a, 212b, 212 c has about the same thickness, while in other embodiments, thethickness of each of layers 212 a, 212 b, 212 c vary. Since thethicknesses of each of layers 212 a, 212 b, 212 c is small compared tothickness d of recessed feature 104, this makes it easier to achieve amating surface 214 that is flush, or very close to flush, with the topsurface of adjacent channel 208.

In some embodiments, dimensional data is collected with regard to theplanarity of mating surface 214 using, for example, optical imaging, alaser scanning, and/or a profilometry techniques. The dimensional datacan be two-dimensional data or three-dimensional data. Such dimensionaldata can be collected, stored and processed using an electronic system,such as the electronic system described in detail below with referenceto FIG. 11. If it is determined that mating surface 214 is planar inshape within a threshold amount (e.g., 5 micrometer surface variation orless) mating surface 214 can be deemed planar enough. If, however,mating surface 214 is not within the threshold amount of planarity, morelayers of filler material 212 can be added or housing section 100 can bereworked to remove some of filler material 212. Since layers 212 a, 212b, 212 c nominally have very small thicknesses and can be addedsequentially, it is more likely that an acceptably planar mating surface214 can be achieved without needing to rework housing section 100.

At FIG. 2E, adhesive 209 is applied onto mating surface 214. Adhesive209 can be a liquid adhesive or an adhesive tape. In some embodiments,adhesive 209 is a polymer-based adhesive or silicon-based adhesive. Insome embodiments, adhesive 209 provides watertight sealing capability.Since mating surface 214 is substantially planar, this increases wettingof adhesive 209 when applied to mating surface 214. That is, makingmating surface 214 substantially planar increases the surface energy ofmating surface 214 compared to the surface energy of adhesive 209,thereby providing increased wetting of adhesive 209. The planar shapedmating surface 214 also reduces or eliminates any gaps that can hinderthe bonding of adhesive 209 to mating surface 214. That is, fillermaterial 212 creates a smooth mating surface 214 for adhesive 209 tobond with. It has been found that adhesives can allow for about 10%variation in surface flatness relative to the thickness of theadhesives. Thus, a 50 micrometer thick adhesive requires less than 5micrometer surface variation. Filler material 212 helps achieve this byfilling in recessed feature 104. The smoother mating surface 214achieved using filler material 212 also allows adhesive 209 to bethinner than if filler material 212 were not used. In particular,adhesive 209 would have to be thick enough to fill in recessed feature104. In cases where adhesive 209 has a fixed thickness, such an adhesivetape, adhesive 209 may not be able to adequately fill recessed feature104, thereby weakening the adhesion of adhesive 209 to housing section100. Note that in some embodiments, adhesive 209 includes multiplelayers of adhesive material.

At FIG. 2F, part 211 is positioned onto adhesive 209. Part 211 can beanother section of housing, or can be an internal component that ishoused within the larger housing structure. Since adhesive 209 isstrongly bonded to housing section 100, part 211 is also strongly bondedto housing section 100. Furthermore, since filler material 212 fills inrecessed feature 104, there are no gaps between housing section 100 andpart 211 for contaminants to become deposited or that can reduce theadhesion integrity between housing section 100 and part 211. Such gapsmay also be cosmetically unappealing if noticeable by a user. Inaddition, such gaps may also allow light to leak between housing section100 and part 211, which may be aesthetically unappealing.

FIG. 2G shows a front view of a portion of housing section 100 afterdepositing filler material 212 and 218 in recessed features 104 and 202,respectively. Each of filler material 212 and 218 can be formed ofmultiple thin layers deposited using the ink jet printing techniquesdescribed above, thereby providing accurate depositing and thicknesscontrol of filler material 212 and 218. For example, the thickness offiller material 218 can be chosen such that the top surface of fillermaterial 218 is substantially flush with the surface of adjacent channel208.

Another potential benefit to adding filler material 212 and 218 tohousing section 100 is that filler material 212 and 218 can addstructural integrity to corner region 112 a of housing section 100. Asconsumer electronic devices become thinner, the housings, such ashousing section 100, are becoming correspondingly thinner. The thinnerhousing walls of housing section 100 may not have enough stiffness toresist bending and flexing during further manufacturing processes thathousing section 100 undergoes. For example, if housing section 100 ismade of a metal material such as aluminum alloy, corner region 112 a canbe susceptible to bending or flexing, especially if housing section 100is thin. Thus, filler material 212 and 218 can act as stiffeners thatstiffen corner region 112 a, thereby making corner region 112 a lesssusceptible to this bending or flexing. In this way, housing section 100can maintain its shape during subsequent manufacturing processes. Thematerial of filler material 212 and/or 218 can be chosen to provide acertain stiffness. For example, filler material 212 and/or 218 can bemade of a stiff polymer ink, such as certain UV curable polymer inks Insome embodiments, corner regions 112 b, 112 c, 112 d of housing section100 also include corresponding filler materials to stiffen all fourcorners of housing section 100.

Methods described herein can also be used to smooth out protrudingfeatures. To illustrate, FIGS. 3A and 3B show a front view and a crosssection view, respectively, of bump 106 that is formed on mating surface102 of housing section 100. Bump 106 can be an unintentionally formedartifact from a machining process or an intentionally formed feature.Bump 106 protrudes a distance p from mating surface 102. That is, bump106 is proud of mating surface 102. Distance p can be very small, e.g.,about 15 micrometers. Bump 106 includes tapered surfaces 106 a thatprotrude a distance less than top surface 106 b of bump 106. Even thoughbump 106 is generally small, it can negatively affect the adhesioncapability of mating surface 102. In particular, an adhesive may notconform well to the shape of bump 106, which can in turn reduce theadhesion capability of the adhesive.

FIGS. 3C-3E show cross section views of bump 106 undergoing a substratesmoothing process in accordance with some embodiments. FIG. 3C showshousing section 100 after filler material 302 is deposited on matingsurface 102 adjacent to bump 106. In some embodiments, filler material302 does not cover top surface 106 b of bump 106, while in otherembodiments a portion of filler material 302 covers top surface 106 b ofbump 106. Filler material 302 can be made of any suitable material andcan be deposited using any suitable technique in order to create a moreplanar overall mating surface 304. That is, filler material 302 smoothesout and makes bump 106 less prominent. In some embodiments, fillermaterial 302 is an ink and is deposited using an ink jet printingprocess. The viscosity and color of filler material 302 can varydepending on design needs, as described above. In some embodiments, thefiller material is viscous enough to conform to the shape of bump 106,and then harden in a final conformed shape. For example, a UV lightsensitive filler material 302 can be exposed to UV light to harden afterfiller material 302 has suitably conformed to the shape of bump 106.

Filler material 302 can be deposited in layers, as described above withreference to FIGS. 2C and 2D. This can provide the extra control neededto provide a substantially planar mating surface 304. For example, afirst layer of filler material 302 can be deposited in liquid form andallowed to conform to the shape of bump 106. Then the first layer offiller material 302 can be allowed to harden either by air drying or byUV light exposure. Subsequent layers of filler material 302 are thendeposited using the similar procedures until filler material 302 takeson a final shape that evens out bump 106 and provides a substantiallyplanar mating surface 304. Since the layers of filler material 302 canbe deposited in very small thicknesses at a time, e.g., 5 to 10micrometer increments, this allows for better shape conformity aroundbump 106.

The planarity of mating surface 304 can be determined by collectingtwo-dimensional data or three-dimensional data as described above. Insome embodiments, the dimensional data of mating surface 304 is comparedto dimensional data of a reference surface. For example, returning backto FIG. 1, dimensional data of another portion along mating surface 102can be collected and used as a reference or target surface. Thedimensional data can correspond to a contour or profile of the referencesurface. It may be important for all portions along mating surface 102,including over bump 106, to have a coplanar shape and orientation suchthat all points along mating surface 102 can match with a correspondingplanar mating surface of a second housing section. Thus, a target can befor mating surface 214 to be coplanar with remaining portions of matingsurface 102.

FIG. 3D shows housing section 100 after adhesive 306 is applied ontomating surface 304. Filler material 302 makes mating surface 304substantially planar, thereby allowing adhesive 306 to create a betterbond with mating surface 304. FIG. 3E shows housing section 100 afterpart 308 is positioned on adhesive 306. In some embodiments, part 308 isanother housing section that mates with housing section 100 to form ahousing for an electronic device. In some embodiments, part 308 is aninternal component that is housed within a larger housing structure.Since adhesive 306 is strongly bonded to housing section 100, part 308is also strongly bonded to housing section 100. Furthermore, sincefiller material 302 surrounds bump 106, there are no gaps betweenhousing section 100 and part 308. Specifically, without filler material302, a gap could form between adhesive 306 and housing section 100around bump 106, which means adhesive 306 could be less securely bondedwith housing section 100. In some embodiments adhesive 306 can be madeof a material sufficient to provide a moisture resistant seal betweenhousing section 100 and part 308. Thus, the elimination of such gap canbe important to assure the integrity of such moisture resistant seal. Inaddition, such a gap could be an entry point for debris and contaminantsthat would eventually weaken the bonding of adhesive 306 to housingsection 100. Such gap could also be noticeable to a user of the finalproduct and negatively affect the cosmetic appearance of the product. Inaddition, such gap could also allow light to leak between housingsection 100 and part 308. This can be especially important if bump ispositioned proximate to a display screen of the electronic device. Inparticular, light leakage around a display screen can interfere with thequality of the display screen.

FIGS. 4A and 4B show a front view and a cross section view,respectively, of a portion of housing section 100 with protrudingfeature 108. In some embodiments, protruding feature 108 includesopenings 401 for accommodating fasteners. Mating surface 402 ofprotruding feature 108 can be configured to mate with a surface of acorresponding second housing section. Thus, mating surface 402 ofprotruding feature 108 is ideally coplanar with mating surface 102 shownin FIG. 1. Note that mating surface 402 is non-contiguous with matingsurface 102. However, both mating surface 402 and mating surface 102 canbe mated with a corresponding second housing section. The shape andorientation of mating surface 102 with respect to mating surface 402 canbe represented as reference contour 403 (or reference plane 403).Reference contour 403 can be acquired by obtaining three-dimensionalmapping data of mating surface 102 using techniques such as thosedescribed above. Dimensional data can also be taken of mating surface402 of protruding feature 108, and compared to reference contour 403 todetermine the difference between the two. This difference corresponds tothe area of filler material required to bring top surface 402 inco-planar alignment with mating surface 102.

It can be important for mating surface 402 to be coplanar with matingsurface 102 in order to provide proper mating and sealing with thesecond housing section. However, mating surface 402 is sloped relativeto reference contour 403. This sloping can cause a gap to form betweenhousing section 100 and the corresponding second housing section whenthey are joined together. As described above, such gaps can benoticeable and detract from the cosmetic appeal of a final product.Debris can also get trapped in these gaps and/or light can leak thegaps.

FIGS. 4C and 4D show a front view and a cross section view,respectively, of protruding feature 108 after undergoing a surfacefilling process, in accordance with some embodiments. FIG. 4C showsfiller material 404 deposited onto protruding feature 108 in sections404 a, 404 b, 404 c, 404 d, 404 e, 404 f that are progressively thickerso as to provide a mating surface 406 that is substantially co-planarwith reference contour 403. In particular, section 404 a is thinnest andsection 404 f is thickest, in accordance with sloped surface 402 ofprotruding feature 108. Since reference contour 403 is coplanar withmating surface 102, mating surface is substantially coplanar with matingsurface 102. In another words, sloped surface 402 is brought intoconformance in a stepwise fashion by depositing filler material 404 onsloped surface 402 in accordance with reference contour 403. In thisway, filler material 404 can be referred to as a shim. Thus, a secondhousing section will be more securing mated with housing section 100.

The thickness of each of sections 404 a, 404 b, 404 c, 404 d, 404 e, 404f of filler material 404 can be controlled using the multilayeredprinting techniques described above. For example, one or a few layers ofink can be deposited to form thinnest section 404 a, while multiplelayers of ink can be deposited to form thickest section 404 f. Theprecise printing methods can also assure that filler material 404 isdeposited only on protruding feature 108 and not on other surfaces ofhousing section 100 or within openings 401, which may be used toaccommodate fasteners.

It should be noted that FIGS. 4C and 4D illustrate only oneconfiguration of a filler material 404 and that other configurationscould be used to form mating surface 406 that is substantially co-planarwith reference contour 403. For example, a continuous filler material,instead of sections 404 a, 404 b, 404 c, 404 d, 404 e, 404 f of fillermaterial 404, can be deposited. In addition, since the printing processcan provide accurate deposition control, sections 404 a, 404 b, 404 c,404 d, 404 e, 404 f can have any suitable shape, such as sections thatrun lengthwise with respect to protruding feature 108 or concentricallyarranged sections.

In some embodiments, the filling process is used to provide a matingsurface based on a reference surface that is on a different plane thatthe mating surface. To illustrate, FIGS. 5A and 5B show perspectiveexternal 501 and internal 503 views, respectively, of housing section100. External view 501 shows external surface 502, and internal view 503shows internal surface 504 of housing section 100. Inlay region 110 ofhousing section 100 corresponds to a region where inlay 505 will beplaced and fixed to housing section 100. Inlay region 110 is recessedwith respect to internal surface 504 and includes opening 506 thatallows viewing of a portion of inlay 505 from external view 501.

Inset 507 shows a close up view of inlay region 110 with recessedsurface 508 that is shaped to accommodate inlay 505. In someembodiments, recessed surface 508 ideally has a shape corresponding to ashape of a surface portion of external surface 502 near opening 506,represented as reference contour 510 (or reference plane 510). This canresult in less offset of inlay 505 with respect to external surface 502once inlay 505 is positioned and fixed within opening 506. However,recessed surface 508 may not correspond with reference contour 510 dueto tolerances or cutter tool mismatching used in machining processes.The extent to which the shape of recessed surface 508 differs fromreference contour 510 can be determined by obtaining and comparingthree-dimensional mapping data of recessed surface 508 and referencecontour 510, as described above. Note that in some embodiments, recessedsurface 508 ideally has a curved shape in accordance with a curvedreference surface portion of external surface 502.

FIG. 5C shows inlay region 110 with filler material 512 deposited onportions of recessed surface 508. In particular, filler material 512 isdeposited in sections 512 a, 512 b, 512 c, 512 d having varyingthicknesses that result in mating surface 514 that is substantiallyparallel with reference contour 510. Sections 512 a, 512 b, 512 c, 512 dcan each be deposited using the multilayered printing techniquesdescribed above, wherein thicker sections include more layers of ink.For example, section 512 d can be thicker than section 512 c, which canbe thicker than section 512 b, which can be thicker than section 512 a.In some embodiments, portion 513 of recessed surface 508 does not haveany filler material 512 deposited thereon.

FIGS. 5D and 5E show external 501 and internal 503 views of housingsection 100 after inlay 505 is positioned over filler material 512 andwithin opening 506. Since mating surface 514 is substantially parallelwith reference contour 510, inlay 505 is substantially flush withexternal surface 502. That is, there is substantially no offset betweena top surface of inlay 505 and external surface 502, resulting in anaesthetically appealing overall external surface 502 of housing section100.

FIG. 6 shows another use for the surface filling techniques describedherein. FIG. 6 shows a perspective view of first housing section 600 andsecond housing section 601, which collectively can form a housing for anelectronic device. First housing section 600 includes cavity 604 thatcan accommodate various components, such as a display assembly. Secondhousing section 601 can be, for example, a cover glass that issubstantially transparent to allow viewing of a display assembly housedwithin cavity 604. First housing section 600 includes lip portion 602that defines a perimeter of housing section 600. Lip portion 602 can besecured to second housing section 601 using, for example, adhesive. Thedimensions of lip portion 602 can be defined by length l.sub.1 and widthw.sub.1, which should optimally be matched with corresponding lengthl.sub.2 and width w.sub.2 of second housing section 601.

One of the problems that may occur due to imperfect manufacturingprocesses is that length l.sub.1 and width w.sub.1 of lip portion 602can vary among product lines of first housing sections 600. In addition,length l.sub.2 and width w.sub.2 of second housing section 601 can varyamong product lines of second housing sections 601. This can causemismatched dimensions of corresponding first housing sections 600 andsecond housing sections 601. For example, length l.sub.1 and widthw.sub.1 of lip portion 602 can be substantially larger than lengthl.sub.1 and width w.sub.1 of second housing section 601. Some tolerancemay be provided, for example, to make room for adhesive(s). However, toomuch space may cause an improper seal between first housing section 600and second housing section 601. In these situations, first housingsection 600 and/or second housing section 601 would typically bescrapped, creating waste in the manufacturing process.

One way to address this problem is to deposit a thin layer of fillermaterial along surfaces of lip portion 602 such that second housingsection 601, can properly mate with lip portion 602. For example, insetview 606 shows a cross section view of a portion of lip portion 602. Asshown, lip portion 602 can be defined by first surface 608 and adjacentnon-parallel second surface 610. First filler material 612 can bedeposited on portions of first surface 608 so as to shorten widthw.sub.1 and/or length l.sub.1 of lip portion 602. First filler material612 can be deposited in multiple thin layers, as described above, untilfirst filler material 612 achieves a desired thickness. In this way, thedimension of lip portion 602 can be modified to match with acorresponding mating surface 605 of second housing section 601. In someembodiments, second filler material 614 is also deposited on secondsurface 610 of lip portion 602. Second filler material 614 can be usedto compensate for any unevenness of second surface 610 with respect to asecond portion of mating surface 605 of second housing section 601. Inthis way, the methods can add thickness to internal vertical andhorizontal surfaces of first housing section 600.

Dimensions, such as length l.sub.1 and width w.sub.1 of lip portion 602and length l.sub.2 and width w.sub.2 of second housing section 601 canbe obtained using three-dimensional mapping techniques described above.For example, a first dimensional mapping operation can be used tocollect length l.sub.1 and width w.sub.1 of lip portion 602 and a seconddimensional mapping operation can be used to collect length l.sub.2 andwidth w.sub.2 of second housing section 601. The data from the first andsecond dimensional mapping operations can be saved in a database andcompared and used to determine a desired thickness of first fillermaterial 612. Similar comparisons can be used to determine a desiredthickness of second filler material 614. In some embodiments, firstfiller material 612 and second filler material 614 are eachsubstantially uniform in thickness. In other embodiments, one or both offirst filler material 612 and second filler material 614 each havevaried thickness to compensate for any non-planarity of first surface608 and/or second surface 610.

FIGS. 7A-7C show cross section views of substrate 700 undergoing asurface filling process in accordance with other embodiments. In someembodiments, substrate 700 is part of an enclosure, such as for anelectronic device. Mating surface 713 can be joined with anothersubstrate using adhesive, fasteners, or both. In this way, substrate 700can be referred to as a primary or base substrate that is configured tojoin or couple with a secondary or auxiliary substrate. FIG. 7A showsrecessed feature 702, which can impede good mating with thecorresponding substrate. Therefore, a filling process can be used tofill recessed feature 702 to be level with external surface 703.However, recessed feature 702 includes undercut surface 704, whichcorresponds to a surface within recessed feature that is obscured byoverhang portion 706. Overhang portion 706 can block undercut surfacefrom being directly deposited or printed on with filler material. Thus,the filler material may not reach and deposit on undercut surface 704,resulting in incomplete filling of recessed feature 702.

One way to address this problem is by using a filler material that has alow viscosity so that the filler material can flow and distribute itselfalong all surfaces within recessed feature 702. If the filler materialis viscous enough, it can flow onto undercut surface 704 while in liquidform and then harden into a solid state, thereby allowing full coverageof surfaces within recessed feature 702. The filler material can beapplied in layers, as described above, with each layer being allowed toflow and distribute within recessed feature 702. In some cases, however,recessed feature 702 may still not be adequately filled due to theunusual shape of recessed feature 702. In this way, recessed feature 702can be deemed not unrepairable or cannot by brought into conformance bydepositing filler material alone.

In some embodiments, the dimensions of recessed feature 702 are modifiedso that a filler material can more easily access all surfaces withinrecessed feature 702. For example, FIG. 7B shows recessed feature 702after a feature modification process. As shown, overhang portion 706 isremoved, thereby providing clear access to surface 708 within recessedfeature 702 and rendering previously unrepairable recessed feature 702as reparable. This modification can be accomplished using any suitablemethod, depending, in part, on the material of substrate 700 and thesize of recessed feature 702. For example, a laser ablation process, amachining process and/or a chemical etching process can be used. In someembodiments where recessed feature 702 is very small, a laser ablationprocess is preferred since laser ablation can generally provide accuratecontrol of amount and location of material removal.

FIG. 7C shows recessed feature 702 after filler material 710 isdeposited within recessed feature 702. In some embodiments, a printingprocess is used, as described above, such that filler material 710 canbe deposited precisely within recessed feature 702 and with controlledamounts. In some embodiments, multiple layers of ink are sequentiallydeposited to form filler material 710. In some embodiments, fillermaterial 710 has a low viscosity such that it can easily conform to theshape of recessed feature 702 and then harden to a rigid material.Filler material 710 can be deposited such that exposed surface 712 offiller material 710 is substantially coplanar, or flush, with externalsurface 703 of substrate 700, forming a substantially planar matingsurface 713. Note that in some embodiments, mating surface 713 is curvedto match with a corresponding curved surface of a mating surface of asecond substrate.

Note that feature modification process used on recessed feature 702 canalso be used to modify the shape of a protruding feature. For example,returning to FIGS. 3A-3E, it may be determined that bump 106 protrudes adistance p too high to provide a sufficiently planar mating surface 304,thereby deemed not reparable solely by depositing filler material. Inthese cases, the shape of bump 106 can be modified to decrease distancep such that filler material 302 can adequately form a substantiallyplanar mating surface 304. In some embodiments, bump 106 is transformedinto a recessed feature that can then be filled with filler material.

FIG. 8 shows flowchart 800 indicating a method for modifying a surfaceof a substrate, in accordance with some embodiments. The substrate canbe a first substrate arranged to couple with a second substrate. Thefirst and second substrates can be made of any suitable materialincluding, but not limited to, one or more of metal, plastic, glass, andceramic. In some embodiments, the first substrate is part of a firsthousing section that is configured to couple with a second housingsection to form a housing for an electronic device. In a particularembodiment, the first and second housing sections are made of metal,such as an aluminum alloy.

At 802, a feature is identified on a mating surface of the firstsubstrate. The mating surface can correspond to a surface of the firstsubstrate that is coupled to the second substrate, either directly orvia one or more adhesive layers. The feature may be in the form of arecess (e.g., divot, scratch, dent, channel) or a protrusion (e.g.,bump, offset portion, ledge) that prevents intimate contact between thefirst substrate and the second substrate. The feature may be a defectthat is unintentionally formed during one or more manufacturingoperation, or may be intentionally formed on the first substrate.

At 804, a determination is made as to whether the feature should bemodified. The feature may have a shape or contour that is not conduciveto depositing a filler material on or around the feature. For example,the feature may include an overhang that blocks deposition of fillermaterial. This blocking can create voids between the filler material andthe first substrate that decreases a bond strength of the fillermaterial with the first substrate. In some embodiments, the feature istoo small to be deposited with filler material. In some embodimentswhere the feature is a protruding feature, the protruding feature mayprotrude a distance too far from the first substrate to provide adequatesmoothing using filler material.

If it is determined that the feature should be modified, at 806 thefeature is modified using a feature modification process. This processcan include increasing the size of a recessed feature so that fillermaterial can adequately fill or more easily fill the recessed feature.If the feature includes an overhang that impeded depositing of fillermaterial, the feature modification process can remove the overhang,allowing access to all surfaces within the feature. If the feature is aprotruding feature that protrudes too far from the first substrate,material from the protruding feature can be removed to shorten theprotruding feature. In some cases, enough material is removed from theprotruding feature to form a recessed feature. The feature modificationprocess can include, but is not limited to, one or more machining, laserablation and/or etching techniques.

At 808, a filler material is deposited in and/or around the feature inaccordance with a reference surface. The filler material can be made ofany suitable material and can be deposited using any suitable technique.In some embodiments, the filler material is deposited using a printingtechnique where the filler material is deposited in very small dropletswith the direction and placement of droplets accurately controlled by aprinter, such as an ink jet printer. In some embodiments, a viscosity ofthe filler material is sufficiently low to allow the filler material tospread and conform to a shape of the feature. The filler material canthen be allowed to harden to a final shape that is conformal with thefeature. In some embodiments where the filler material is UV lightreactive, UV light can be used to harden or accelerate hardening of thefiller material. In some embodiments, the filler material is chosen tohave a higher viscosity such that the filler material does not spreadtoo much and overflow onto adjacent surfaces of the substrate. In someembodiments, the filler material is deposited in multiple layers until afinal thickness of filler material is achieved. The multiple layerdepositing can allow for accurately achieving a final desired thicknessof filler material. In some cases, each layer of filler material issequentially be allowed to conform to a shape of a portion of thefeature and then hardened.

The reference surface can refer to a surface having a two-dimensional orthree-dimensional shape and/or orientation of a desired final shape ofthe mating surface. The reference surface can be a substantially planarsurface or a non-planar surface, such as a curved surface. In someembodiments, the reference surface is adjacent the mating surface suchthat when the filler material is deposited, the filler material makesthe mating surface substantially flush with the adjacent referencesurface. In some embodiments, the reference surface is a planar surfacethat is coplanar with another non-contiguous mating surface of thesubstrate. In some embodiments, the reference surface corresponds to athree-dimensional shape of a corresponding mating surface of the secondsubstrate. If the feature is a recessed feature, the filler material canfill in the recessed feature and build up the recessed feature to adesired height. If the feature is a protruding feature, the fillermaterial can be deposited around the feature to smooth out and make themating surface take on a final desired shape, such as a substantiallyplanar shape.

In some embodiments, three-dimensional data of the reference surface isobtained by imaging, scanning and/or mapping techniques. In someembodiments, an imaging device is used to optically scan and collectimages of the reference surface. In some embodiments, a contact-basedtechnique, such as surface profilometry, is used. In some embodiments, alaser scanning technique, such as laser dot scanning, is used. In someembodiments, a combination of imaging, laser scanning and/orcontact-based techniques are used. In some embodiments, thethree-dimensional data is computer-simulated data.

At 810, an adhesive is optionally applied onto the mating surface. Theadhesive can be a layer of adhesive material, such as a UV activatedliquid adhesive or adhesive tape. In some embodiments, multiple layersof adhesive are used. The thickness of the adhesive can be optimallysmall so as to take up as little space as possible, yet provide goodbonding performance. The thickness of the adhesive will depend on thetype of adhesive(s) and the material of the first and second substrates.

At 812, the first substrate is coupled at the mating surface with thesecond substrate. If an adhesive is used, the first substrate is coupledwith the second substrate via the adhesive. In some embodiments, thefirst substrate is coupled with the second substrate with one or morefasteners, such as screws, bolts, etc. In some embodiments, acombination of adhesive and fastener(s) are used. The filler material onthe mating surface can compensate for any pre-formed defects on themating surface and prevent a gap associated with the feature fromforming between the first substrate and the second substrate.

FIG. 9 shows flowchart 900 indicating another method for modifying asurface of a substrate, in accordance with some embodiments. At 902, ashape of a mating surface is determined. The mating surface cancorrespond to a surface where another substrate, such as a secondhousing section, an inlay or another type of part, is mounted or coupledto the substrate. The shape can be a two-dimensional shape or athree-dimensional shape of the mating surface. The shape can bedetermined using any suitable method, including obtaining data usingnon-contact methods and/or contact methods. Non-contact methods mayinclude imaging and/or laser scanning techniques. Contact methods caninclude profilometry or other techniques. In some cases, a combinationof non-contact and contact methods is used. A computing device can storedata corresponding to the shape of the mating surface.

At 904, a shape of a reference surface is determined. The referencesurface has a shape that corresponds to an ideal shape of the matingsurface. The reference surface can have any desirable shape, such as aplanar shape or a curved shape. The reference surface can correspond toshape of another surface portion of the substrate. For example, thereference surface can correspond to an adjacent or non-adjacent portionof the mating surface. In some embodiments, the shape of the referencesurface corresponds to a surface of the substrate opposite the matingsurface, such as inlays as described above with reference FIGS. 5A-5E.The shape of the reference surface can be obtained using any suitablemethod such as imaging, laser scanning and/or profilometry. In someembodiments, the shape of the reference surface is obtained the same wayas obtaining the shape of the mating surface. In some embodiments, theshape of the reference surface determined by simulated data—that is,data obtained by computational methods.

At 906, filler material is deposited on the mating surface such that themating surface takes on the shape of the reference surface. This can beaccomplished by determining the difference between the shape of thereference surface and the shape of the mating surface, then depositingthe filler material on the mating surface at appropriate locations andin appropriate amounts until the mating surface attains the shape of thereference surface. In some embodiments, the mating surface has adistinctive feature, such as a recessed feature or a protruding feature,which is deposited on and/or around with the filler material. In someembodiments, the mating surface is sloped or otherwise misshaped incomparison to the reference surface. In some embodiments, sections offiller material having different thicknesses are deposited on the matingsurface. After the filler material is deposited and the mating surfacetakes on the shape of the reference surface, the mating surface is readyto be coupled with another substrate, either directly or using one ormore adhesives.

FIG. 10 shows flowchart 1000 indicating a further method for adjusting asurface of a substrate. The surface of the substrate can be a matingsurface that is to be joined or coupled with another substrate. At 1002,a contour of the surface is compared to a contour of a referencesurface. The reference surface can be on the same plane of the surfaceor on a different plane that the surface. The reference contour can be aplanar or non-planar (e.g., curved).

At 1004, a portion of the surface can be identified as having acorresponding surface contour that is out of conformance with respect tothe reference contour based upon the comparing. For example, the portionof the surface can be have include a bump that protrudes a distancebeyond a predetermined threshold value, or a divot or recess thatrecesses a distance beyond a predetermined threshold value. At 1006, itis determined whether the portion of the surface includes a bump ordivot. The portion of the surface can be characterized as a bump whenthe corresponding surface contour is proud of the reference contour anda divot otherwise.

At 1008, if it is determined that the portion of the surface has a bump,the corresponding surface contour is brought into conformance bydepositing filler material around the bump. In some cases, some of thefiller material is also deposited on top of the bump. At 1010, if it isdetermined that the portion of the surface has a divot, thecorresponding surface contour is brought into conformance by depositingfiller material within divot.

FIG. 11 is a block diagram of electronic system 1100 suitable forcontrolling some aspects of the depositing processes described above.Electronic system 1100 can represent a computing system in conjunctionwith one or more of the surface inspecting systems described above(e.g., optical, profilometry, and/or laser scanning systems). Electronicsystem 1100 includes processor 1102 that pertains to a microprocessor orcontroller for controlling the overall operation of electronic system1100. Electronic system 1100 contains instruction data pertaining toinstructions in a file system 1104 and cache 1106. File system 1104 is,typically, a storage disk or multiple storage disks. File system 1104typically provides high capacity storage capability for electronicsystem 1100. However, since the access time to file system 1104 can berelatively slow, electronic system 1100 can also include cache 1106.Cache 1106 can be, for example, Random-Access Memory (RAM) provided bysemiconductor memory. The relative access time to cache 1106 can besubstantially shorter than for file system 1104. However, cache 1106 maynot have the large storage capacity of file system 1104. Further, filesystem 1104, when active, can consume more power than cache 1106. Thepower consumption can be a concern when electronic system 1100 is aportable device that is powered by battery 1124. Electronic system 1100can also include RAM 1120 and Read-Only Memory (ROM) 1122. ROM 1122 canstore programs, utilities or processes to be executed in a non-volatilemanner. RAM 1120 can provide volatile data storage, such as for cache1106.

Electronic system 1100 can also include user input device 1108 thatallows a user of electronic system 1100 to interact with electronicsystem 1100. User input device 1108 can take a variety of forms, such asa button, keypad, dial, touch screen, audio input interface,visual/image capture input interface, input in the form of sensor data,etc. Still further, electronic system 1100 can include display 1110(e.g., screen display) that can be controlled by processor 1102 todisplay information to the user. In some embodiments, display 1110provides data or images collected from the inspecting system. Data bus1116 can facilitate data transfer among at least file system 1104, cache1106, processor 1102, and coder/decoder (CODEC) 1113. CODEC 1113 can beused to decode and play multiple media items from file system 1104 thatcan correspond to certain activities taking place during a particularprocess. Processor 1102, upon a certain event occurring, supplies mediadata (e.g., audio file) for a particular media item to CODEC 1113. CODEC1113 can then produce analog output signals for speaker 1114. Speaker1114 can be a speaker internal to electronic system 1100 or external toelectronic system 1100. For example, headphones or earphones thatconnect to the electronic system 1100 would be considered an externalspeaker.

Electronic system 1100 can also include network/bus interface 1111 thatcouples to data link 1112. Data link 1112 can allow electronic system1100 to couple to a host computer or to accessory devices. Data link1112 can be provided over a wired connection or a wireless connection.In the case of a wireless connection, network/bus interface 1111 caninclude a wireless transceiver. The media items (media assets) canpertain to one or more different types of media content. In oneembodiment, the media items are audio tracks (e.g., songs, audio books,and podcasts). In another embodiment, the media items are images (e.g.,photos). However, in other embodiments, the media items can be anycombination of audio, graphical or visual content. Sensor 1126 can takethe form of circuitry for detecting any number of stimuli. For example,sensor 1126 can include any number of sensors for monitoring a surfacecharacterization operation such as a Hall effect sensor responsive toexternal magnetic field, an audio sensor, a light sensor such as aphotometer, etc.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona non-transitory computer readable medium for controlling manufacturingoperations or as computer readable code on a non-transitory computerreadable medium for controlling a manufacturing line. The non-transitorycomputer readable medium is any data storage device that can store data,which can thereafter be read by a computer system. Examples of thenon-transitory computer readable medium include read-only memory,random-access memory, CD-ROMs, DVDs, magnetic tape, optical data storagedevices, and carrier waves. The non-transitory computer readable mediumcan also be distributed over network-coupled computer systems so thatthe computer readable code is stored and executed in a distributedfashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not target to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

What is claimed is:
 1. An electronic device assembly comprising: a glasshousing member defining a mating surface; and a polymer-based coatingdisposed on at least a portion of the mating surface and comprising: afirst coating portion comprising a first number of coating layers anddisposed along a first region of the mating surface, the first region ofthe mating surface recessed a first distance with respect to a referenceportion of the mating surface; and a second coating portion comprising asecond number of coating layers different from the first number ofcoating layers and disposed along a second region of the mating surface,the second region of the mating surface recessed a second distance,different than the first distance, with respect to the reference portionof the mating surface.
 2. The electronic device assembly of claim 1,wherein: the first distance is greater than the second distance; thefirst coating portion is thicker than the second coating portion; andthe first number of coating layers is greater than the second number ofcoating layers.
 3. The electronic device assembly of claim 2, wherein:the first region of the mating surface abuts the second region of themating surface; and the first region of the mating surface and thesecond region of the mating surface define a sloped portion of themating surface.
 4. The electronic device assembly of claim 2, whereinthe first region of the mating surface abuts a protruding feature on themating surface.
 5. The electronic device assembly of claim 2, whereinthe first distance is less than or equal to 50 microns.
 6. Theelectronic device assembly of claim 2, wherein an upper surface of thefirst coating portion and an upper surface of the second coating portionare substantially coplanar with the reference portion of the matingsurface.
 7. The electronic device assembly of claim 2, wherein thepolymer-based coating is transparent.
 8. The electronic device assemblyof claim 1, wherein: the glass housing member is a first housing memberand the mating surface is a first mating surface; and the electronicdevice assembly further comprises: a second housing member defining asecond mating surface; and an adhesive disposed between thepolymer-based coating and the second mating surface and bonding thefirst housing member to the second housing member.
 9. A methodcomprising: identifying a first region of a mating surface of a glasshousing member as recessed a first distance with respect to a referenceportion of the mating surface; identifying a second region of the matingsurface as recessed a second distance, different than the firstdistance, with respect to the reference portion of the mating surface;and applying a polymer-based coating to the mating surface, comprising:applying a first number of coating layers along the first region of themating surface thereby forming a first portion of the polymer-basedcoating; and applying a second number of coating layers, different fromthe first number of coating layers, along the second region of themating surface thereby forming a second portion of the polymer-basedcoating.
 10. The method of claim 9, wherein an upper surface of thefirst portion of the polymer-based coating and an upper surface of thesecond portion of the polymer-based coating are substantially coplanar.11. The method of claim 10, wherein the reference portion of the matingsurface is substantially planar.
 12. The method of claim 10, whereineach of the first number of coating layers and each of the second numberof coating layers has a same thickness.
 13. The method of claim 9,wherein: the glass housing member is a first housing member; and themethod further comprises coupling a second housing member to the firsthousing member.
 14. The method of claim 13, wherein the operation ofcoupling the second housing member to the first housing membercomprises: applying an adhesive to the polymer-based coating of thefirst housing member; and positioning the second housing member on theadhesive.
 15. An electronic device comprising: a housing comprising: aglass first housing member defining a mating surface; a polymer-basedcoating disposed on at least a portion of the mating surface andcomprising: a first coating portion comprising a first number of coatinglayers and disposed along a first region of the mating surface, thefirst region of the mating surface recessed a first distance withrespect to a reference portion of the mating surface; and a secondcoating portion comprising a second number of coating layers differentfrom the first number of coating layers and disposed along a secondregion of the mating surface, the second region of the mating surfacerecessed a second distance, different than the first distance, withrespect to the reference portion of the mating surface; and a secondhousing member coupled to the glass first housing member; and a displaypositioned within the housing.
 16. The electronic device of claim 15,wherein: the mating surface is a first mating surface; the secondhousing member defines a second mating surface; and the housing furthercomprises an adhesive disposed between the polymer-based coating and thesecond mating surface and bonding the glass first housing member to thesecond housing member.
 17. The electronic device of claim 15, wherein:the first distance is greater than the second distance; the firstcoating portion is thicker than the second coating portion; and thefirst number of coating layers is greater than the second number ofcoating layers.
 18. The electronic device of claim 17, wherein: thefirst region of the mating surface abuts the second region of the matingsurface; and the first region of the mating surface and the secondregion of the mating surface define a sloped portion of the matingsurface.
 19. The electronic device of claim 17, wherein the first regionof the mating surface abuts a protruding feature on the mating surface.20. The electronic device of claim 17, wherein the first distance isless than or equal to 50 microns.
 21. The electronic device of claim 17,wherein an upper surface of the first coating portion and an uppersurface of the second coating portion are substantially coplanar withthe reference portion of the mating surface.
 22. The electronic deviceof claim 17, wherein the polymer-based coating is transparent.